Television system



Patented May 7, 1940 TELEVISION SYSTEM Rudolf Urtel, Berlin, Germany, assignor to'Telefunken Gesellschaft-fiir Drahtlose Telegraphic m. b. H., Berlin, Germany, a corporation of Germany Application March 17 In Germany 4 Claims.

' This invention relates to television systems and in particular, to the synchronizing method for use with skip-line or interlacing television I systems.

For the transmission of picturesin television it is known to use the socalled line skip method residing in that the lines 1, 2, 3 etc. of the'picture to be transmitted, are sent, out in two series,

, the first of which covering only the lines "1, 3, 5

etc. while the second one contains the lines 2,

4, 6 etc. and will be sent out only following the transmission of all lines of the first'series. This known method may also be applied in such manner that the picture is divided into three or 12'- series of lines, whereby in case of three series of lines the first series covers the lines 1, 4, 7 etc., the second series the lines 2, 5, 8 etc. and the third one covers the lines 3, 6, 9 etc. In the case of n-series of lines, the first series of lines in- 0 eludes the lines 1, n+1, 2n+1 etc. while the second series includes the lines 2-, n+2, 2n+2, etc. This method makes it possible at equal width of the frequency band required for the picture transmission, to multiply the scanning frequency 5in the direction at right angle to, or almost at right angle, to the direction of 'the line, thereby considerably reducing the. highly disturbing impression of flickering at the receiver. The methodas described, requires a reproducingarrangement at the receiver in which the firstline of each series of lines (seen in'the'direction at right angle or almost at right angle to the line'direc tion) starts at another place of the reproducing screen. This is especially desirable if for instance a Braun tube is to be employed for reproducing the image. In this case, a deflection potential is required having a different starting point at each series of lines, and which is permitted to return to the same voltage value only w after the completion of n-series of lines. However, such deflection voltages to be produced require considerable means.

Accordingly, it is the object of my invention to provide a new and novel method of improving L5 synchronizing of television receiving systems in which skip-line or interlaced scanning is used.

Referring now to the drawing, in which Fig. 1 shows schematically the simple skipline scanning;

0 Fig. 2 shows schematically multiple skip-line scanning; and

Fig. 3 shows in box diagram my arrangement for improving the synchronizing of skip-line scanning; my invention will be described in de- 5 tail.

, 193s, SerialNo. 69,318 March 25, 1935 But it is possible to overcome this disadvantage when resorting to aline skip method which may be designated as line skip method operating with line division. The functioning of this method will be elucidated with reference to Fig- 6 ure 1 of the drawing: representing the relative position of two series of lines (11:2) on thereceiving screen. ,For the sake of simplification in this'Figure I an image consisting of only Qlines is assumed whereby the first series includes the 1 0 lines 1, 3, 5, 7 and the first half of the 9th line (these lines are indicated in Figure l by full lines), while the second series of lines consists of a half line which may beconsidered as the second half of the. 9th line, but displaced relative 15 to the first half by the entire height of the picture, and this second series furthermore includes the lines 2, 4, fi'and '8' (the lines'of -the second series are indicated in Figure 1 by dash lines) 1 Following the transmission of the second series of lines i. eafter the completion of line 8 in Figure 1, the first series of lines will again be transmitted beginning at the left end of line 1. It can be readily seen that in this special line skip method. the scanning movement of the luminous spot in 25 the vertical direction has to start always from the same initial point, since the starting point pif of the first series of lines and the starting point pg of the second line series are situated in the same height while furthermore the duration "'of at each series of lines is the same. This method maybe also correspondingly ap-f last mentioned line skip method, it is to be borne 1) the impulse which interrupts the 9th line'and leads to the beginning of the second line series, follows the last line impulse at a distance equal to f channels.

the duration of a half line and during which the 9th line has been initiated, while the line seriesimpulse beginning at the termination of the 8th line and through which the first line series will again be started, is displaced as to time from the line impulse of the 8th line by an amount equal to a total duration .of, the line. This tactic of importance since that circuit of the receiver which responds to the line series impulse behaves difierently in accordance as to; whether a line imptuse appeared at a preceding halfor total duration of the line.

A suggestion to overcome thi difiiculty resides in providing an auxiliary generator oscillating during the last line of each line series, and which produces an impulse in the center of each line at n=2, and after and ,4; of the duration of the line at 11:3, said impulse serving tdsimulate for the circuit to respond to the line series impulse, identical conditions at the termination of each line series.

Furthermore, before each line series impulse, care can be taken by means of a readiness impulse, that the line series impulse always finds that circuit in the same state which is to be excited by said line series impulse.

Such auxiliary measures are dispensed with in accordance with the invention, in that the line impulse and the line series impulse are transmitted to the receiver on separate transmission It is to be preferred that the line series impulse having a frequency of 5000 in case of a picture of 200 lines and picture transmissions per second, be sent out on the sound transmission channel i. e. over the transmission line or carrier Wave on which the sounds accompanying the picarrangement constructed in accordance with the ture reproduction are-transmitted, while the line series impulse having a frequency of 50 at n=2 and 25 pictures per second, be transmitted on the picture transmission channel, or on the picture transmission carrier wave as shown schematically in the block diagram of Fig. 3. In the receiver, the arrangement serving for the release of the line deflection and that which releases the line series deflection are placed at separate transmission channels, namely according to the abovementioned suggestion, the line deflection arrangement to be placed at the sound transmission channel, the line series deviation arrangement at the picture transmission channel. In a circuit invention, for transmitter and receiver, the aforementioned auxiliary means are dispensed with while avoiding at the same time with absolute assurance, a relative displacementof the two line series.

What I calm is: 1. The method of transmitting television signals which includes the steps of transmitting over a first channel electrical signals representative of an optical image to be transmitted, transmitting over a second channel electrical signals representative of accompanying sound energy related to said optical image, transmitting over said first channel electrical signals related to the 1 synchronous reproduction of said optical image, and transmittmg over said second channel other electrical signals also related'to the synchronous reproductions of said optical image, said other electrical signals having a different character than said third named electrical signals related to the synchronous reproduction.

2. In a television system wherein is provided two related transmitters, the method of trans? mitting pictures which includes the steps of actuating one of said transmitters both by signals representative of the picture to be transmitted and by synchronizing signals of a predetermined character, and actuating the other of said two transmitters both by signals representative of accompanyingsound energy related to said picture and by synchronizing signals of a different char-- acter from those of said first named synchronizing signals.

3. In a television'system wherein is provided two related transmitters, mitting pictures which includes the steps of actuating one of said transmitters both by signals representative of the picture to be transmitted and by synchronizing signals of a predetermined frequency, and actuating the other of said two transmitters both by signals representative of ,accompanying sound energy related to said picture and by synchronizing signals of a different frequency from the predeterminedfrequency of said first named synchronizing signals.

4. In a television system wherein is provided two related transmitters, the method of transmitting pictures which includes the steps of actuating one of said transmitters both by signals representative or the picture. to be transmitted. and by frame synchronizing signals, and actuating 1 the other of said two transmitters both by signals.

representative of accompanying sound energy the method of transrelated to said picture and by line synchronizing I signals. I

'RUDOLF URTEL. 

